The research program proposed in this application is to understand three levels of regulation of P. falciparum (Pf) ribonucleotide reductase--the allosteric control of substrate catalysis, subunit interaction and the iron/tyrosine redox center and to use this fundamental information in the design and testing of specific antimalarial agents. Malaria remains one of the leading causes of death worldwide, being responsible for more than 2 million deaths per year. The increasing incidence of drug resistant malaria makes the development of new approaches to antimalarials a high priority. RR is a two subunit, cell cycle regulated, iron and oxygen dependent allosteric enzyme that is the first committed step in DNA replication catalyzing a radical mediated 2' reduction of ribonucleoside diphosphates to deoxyribonucleoside diphosphates. Agents that inhibit RR are known to inhibit growth patterns of P. falciparum. RR is therefore a prime target for the development of specific antimalarial agents. In this research, we plan to l) Utilize recombinant Pf RR to characterize the unique biochemical properties of the enzyme. 2) Design and synthesize peptides, peptide-mimetics and constrained peptides that disrupt the subunit interaction and test these RR inhibitors in Pf infected red cell cultures 3) Analyze the structure-function-activity properties of classes of compounds that destroy the iron/tyrosine redox center of the enzyme and test these agents in Pf infected red cell cultures.